The present disclosure relates to vehicle bumper structures and, particularly, to vehicle bumper structures with energy absorbing features.
Vehicle bumper structures frequently contain energy absorbers which are constructed to crush or buckle on impact with a predetermined rate of resistance and energy absorption. The energy absorbers can be in the form of a molded plastic base mounted on the forward facing surface of a laterally extending reinforcement beam coupled to a vehicle frame structure. A plurality of forward projecting, hollow lobes (also referred to as “crush lobes”) are formed in and extend horizontally outward from the base. The lobes are spaced across the lateral extent of the base so as to cover substantially the entire forward surface of the vehicle bumper.
The shape and size of the individual lobes are designed to provide a predetermined amount of resistance force and energy absorption when the vehicle bumper contacts an object, such as a leg of a pedestrian. The buckling or crushing of the lobes at the point of impact with the pedestrian's leg is designed to minimize injury to the pedestrian by absorbing impact energy.
The lobes typically are in the form of a hollow box-like structure with top and bottom shear walls and left and right side shear walls joined at corner edges and at an outer, forward facing end by a closed front wall.
The material and thickness of the lobes can be chosen to provide a predetermined amount of resistance and energy absorption through controlled buckling or crushing of the lobes. Toward this end, small apertures are formed in various locations on each lobe to provide controlled buckling of the lobe. For example, apertures can be formed at the corner edges of the front wall and one or more of the top, bottom or side shear walls. Similarly, apertures can be formed at the bottom corners of each lobe where the top, bottom and side shear walls join to the base.
While the buckling of one or more lobes subjected to impact forces presents a predetermined design amount of resistance followed by a controlled buckling, once the lobe begins to buckle, resistance and energy absorption falls off rapidly. The bottom located apertures between the base and the bottom edges of the top, bottom and side shear walls of each lobe can provide a second peak buckling resistance force before further buckling of the lobe commences.
It will be desirable to provide a vehicle bumper structure with energy absorption features which has increased peak force resistance until buckling with less effect on other local impact positions of the vehicle bumper.